OUTLOOK, Wash. -- Three dairies in the Lower Yakima Valley say an Environmental Protection Agency report targeting them for nitrate pollution of groundwater is based on incomplete data and inaccurate assumptions.

"Groundwater is a very complex issue. If you look at nitrates there are lots of other sources that contribute to them and the EPA report was primarily targeted at dairies," Dan DeRuyter, co-owner of George DeRuyter & Sons Dairy, said.

The EPA did not look as closely at other sources of nitrates such as septic systems, nitrate applications by farmers and poorly constructed wells, DeRuyter told Capital Press. Nitrate is soluble and can move through soils from any sources, according to the EPA.

The 307-page report also fails to account for heavy nitrogen applications made years ago when sugar beets were a popular crop in the area, Adam Dolsen, owner of Cow Palace Dairy, said.

EPA began the study in 2009 following a report from the state departments of Agriculture, Ecology and Health, the Yakima County Public Works Department and EPA that recommended more work to identify the sources of nitrate contamination.

A screening analysis determined 65 percent of the valley's nitrates were produced by livestock (mainly dairies), 30 percent were from irrigated crops, 3 percent were from septic systems and 2 percent were from the atmosphere, said Mike Cox, an EPA environmental scientist.

"We looked at sources in each category to see if we could link them to downgradient wells and that's where our general conclusion was -- that the five dairies in the report are likely sources," said Tom Eaton, director of EPA's Operations Office in Olympia.

Samples were taken from more than 331 residential wells, 29 other wells, 12 dairy lagoons, dairy-applicated and non-applicated fields, five dairy manure piles and three wastewater treatment plants. Nitrate levels were above EPA residential drinking water standards.

The EPA is accepting public comment on the report until Nov. 30.

Meanwhile, confidential discussions are taking place between attorneys for the EPA and the dairies addressing what the dairies can do to supply safe drinking water to area residents, Eaton said. The talks include long-term monitoring and how the dairies can better control sources of nitrates.

Initial examination of the report shows some findings may not be supported by science, said Henry Bosma, co-owner of Liberty Dairy.

"We have serious questions but we will continue to work with EPA, other stakeholders and all our neighbors to ensure this region has clean drinking water," he said.

Cox said the report was reviewed by EPA and USDA scientists. The directors of the state departments of Agriculture and Ecology and the state conservationist of the NRCS all commented favorably on the EPA report.

Liberty, Cow Palace and George DeRuyter & Sons issued a news release saying the EPA targeted area dairies, including them.

"While the dairies identified in the study have had only a few days to begin to understand its many details, conclusions and assumptions, this study builds on the mutual goals of the EPA and the region's dairies to assure safe drinking water," said Jay Gordon, executive director of the Washington State Dairy Federation. "We will be working on an agreed upon plan to assess operational changes necessary to provide additional protection of groundwater quality."